First Report of Phytophthora pseudosyringae on Chestnut Nursery Stock in Spain

Abstract

Phytophthora pseudosyringae causes stem necrosis and collar rot of deciduous tree species (Quercus spp., Fagus silvatica, and Alnus glutinosa) in several European countries (1,2). In November 2006, we received diseased Castanea sativa seedlings from a nursery in Galicia (northwest Spain). These plants had tongue-shaped necroses of the inner bark and cambium. Reddish, sunken lesions occurred on the surface of the bark, either in the stem base or higher on the stem. Tissue from the leading edge of the lesions was transferred to a selective V8 agar medium (4) and incubated for 7 days at 20°C in the dark. A Phytophthora sp. was isolated, transferred to cornmeal agar (CMA) and V8 agar, and incubated in the dark. Colonies were appressed with stellate to rosaceous growth patterns on CMA and stellate, limited aerial mycelium on V8 agar. Growth on V8 occurred from 2 to 25°C with an optimum at 20°C and a radial growth rate of 4.5 mm per day at 20°C. Chains of inflated spherical to deltoid hyphal swellings with radiating hyphae were abundantly produced in water (2). Chlamydospores were not observed on agar media. The deciduous, sympodial, semipapillate, rarely bipapillate sporangia with pedicels had a length/breadth average ratio of 1.55. Oogonia, antheridia, and oospores were produced within a single culture. Oogonia were spherical and smooth walled, antheridia were predominantly paraginous, but some were amphyginous, and oospores were plerotic that turned golden yellow with age (2). Internal transcribed spacer (ITS)-rDNA and mitochondrial DNA (mtDNA) regions were amplified by nested-PCR and sequenced with DNA extracted from mycelium. The amplicon sizes obtained were similar to those reported for P. pseudosyringae (2,3). DNA sequences showed 99 to 100% homology with those previously identified as P. pseudosyringae and deposited in GenBank. Pathogenicity of the isolate was confirmed by inoculating 10 C. sativa seedlings, as well as three detached leaves from each of another 10 young plants growing in containers. For the seedlings, one shallow cut was made into the bark on the main stem. A colonized agar plug was inserted beneath the flap that was sealed with Parafilm. Unwounded and wounded detached leaves of C. sativa were dipped into a zoospore aqueous suspension (1 × 105 zoospores ml–1) for 10 s., seedlings and leaves were incubated at 20°C and 95% humidity for 60 and 7 days, respectively. After 7 days, foliar lesions that developed exceeded 25 mm, and the pathogen was consistently reisolated. Leaves inoculated with sterile water did not develop symptoms. On inoculated seedlings, the external surface of the bark was reddish and sunken. Stem lesions progressed bidirectionally from the wound. P. pseudosyringae was recovered from inoculated seedlings but not from controls. On the basis of its unique combination of morphological and physiological characters, pathogenicity, and ITS and mtDNA sequences, the Phytophthora isolated from chestnut was identified as P. pseudosyringae. To our knowledge, this is the first report of P. pseudosyringae on C. sativa in Spain. References: (1) EPPO Reporting Service. Online publication. No. 10 2005/162, 2005. (2) T. Jung et al. Mycol. Res. 107:772, 2003. (3) F. N. Martin et al. Phytopathology 94:621, 2004. (4) C. Pintos Varela et al. Plant. Dis. 87:1396, 2003.

Diversity of Phytophthora Species Involved in New Diseases of Mountain Vegetation in Europe with the Description of Phytophthora pseudogregata sp. nov.

“…The wide spread of P. pseudosyringae in different mountain and subalpine formations and its involvement in several new diseases highlight the polyphagous nature of this invasive pathogen and its aerial lifestyle. This agrees with previous studies conducted in mountain environments in Asia, Europe, North and South America [14,32,34,[55][56][57][58][59][60][61]. Phytophthora pseudosyringae is the key species in the aetiology of aerial infections detected in high-altitude shrubs and heaths such as blueberry, dwarf pine, juniper, rhododendron and alpine willow formations; these shrubs are characterized by creeping behaviour with very limited heights above the ground, this habitus could favour the attack of Phytophthora sporangia and zoospores.…”

Comparative Genomic and Proteomic Analyses of Three Widespread Phytophthora Species: Phytophthora chlamydospora, Phytophthora gonapodyides and Phytophthora pseudosyringae

“…), alder (Alnus spp. ), Japanese larch (Larix kaempferi), sweet chestnut (Castanea sativa), horse chestnut (Aesculus hippocastanum), and shrubs (Vaccinium myrtillus) [23][24][25][26][27]. In a recent metabarcoding study, Ph.…”

Uncovering the hidden hosts: Identifying inoculum reservoirs for Phytophthora pseudosyringae in Nothofagus forests in Chile

“…P. pseudosyringae was described in 2003 as the causal agent of root and collar rot on beech ( Fagus sylvatica ) and alder ( Alnus glutinosa ) in Germany, and isolated from forest soils in France, Germany and Italy (Jung et al., 2003). Since its description, the pathogen has been found causing cankers in beech in Italy (Motta et al., 2003) and affecting chestnut seedlings in a nursery in Spain (Varela et al., 2007). In the UK, P .…”

“…P. pseudosyringae was described in 2003 as the causal agent of root and collar rot on beech (Fagus sylvatica) and alder (Alnus glutinosa) in Germany, and isolated from forest soils in France, Germany and Italy (Jung et al, 2003). Since its description, the pathogen has been found causing cankers in beech in Italy (Motta et al, 2003) and affecting chestnut seedlings in a nursery in Spain (Varela et al, 2007). In the UK, P. pseudosyringae was detected in N. obliqua and N. alpina (Scanu et al, 2012), causing a decrease in the vigour of the crown due to defoliation, development of epicormic shoots associated with bark cracking, and twig blight.…”